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1.Can energy become matter?
Yes
✓
No
✓
2.If you were moving just below the speed of light, could you see light moving beside you, moving slightly faster than you?
Yes
✓
No
✓
The light would still appear to move at the speed of light
3.Does gravity affect time?
Yes
✓
No
✓
4.Which of these things act like a wave sometimes?
Energy
✓
Light
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Matter
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All of the above
✓
5.Can something have infinite density?
Yes
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No
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Called a singularity
6.Is the speed of light the same traveling through every medium?
Yes
✓
No
✓
7.As an object approaches the speed of light, what does the mass approach?
Zero
✓
Infinity
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Mass does not change
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Simultaneously zero and infinity
✓
8.How big is the universe?
Finite
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Infinite
✓
We don't know
✓
9.Can matter emerge spontaneously from a vacuum?
Yes
✓
No
✓
https://en.wikipedia.org/wiki/Vacuum_energy
10.Two spaceships leave Earth in opposite directions, each traveling 0.9 times the speed of light. Could these ships communicate with each other?
Yes
✓
No
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Even though, from Earth, these spaceships would appear to be moving away from each other at 1.8 times the speed of light, the relative speed between them would be less than the speed of light
11.Photons of light approach two slits. How do they travel through the slits?
They travel through one slit or the other
✓
They travel through both simultaneously
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It depends on if they are observed while traveling through
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Of course, to even attempt to answer the question you have to clarify what is being asked. We can answer how big the observable universe is, for instance.
To answer any question you must know the definitions of the words in the question.
https://en.wikipedia.org/wiki/Universe
"The universe (Latin: universus) is all of space and time and their contents, including planets, stars, galaxies, and all other forms of matter and energy."
True, but for many things the scientific definition differs from popular usage or laymen's terms. When people ask how big the universe is, they often mean the observable universe.
In question 7. you're referring to "relativistic mass" as just "mass". It gives the quiz-taker the false idea that an objects mass changes with time, which it does not. "Relativistic mass" is an abstract concept taught to students to simplify the inherently confusing nature of relativity, but that's it, a mathematical concept abstracted from reality.
Highly suggest everyone watch these two videos on the topic:
However, there is no indication in the way the question is worded that this is referring to rest mass nor invariant mass.
If the observer measuring the mass of the object was in the same reference frame as the object, and thus not observing any change in mass, the observer would also ostensibly not be observing any change in the speed of the object. So, at least to me, the question is not misleading.
Remember E=mc^2 which absolutely applies here: as a mass approaches the speed of light, its energy increases, but this could be equivalently interpreted as an increase in mass, tending towards infinity.
Alternatively, as the object approaches the speed of light, the force required to accelerate it at a constant rate approaches infinity (because you need infinite energy to make a nonzero mass move at the speed of light). In this interpretation, because acceleration is constant and force approaches infinity, then by Newton’s 2nd, the object’s mass must be approaching infinity.
I think it’s important to remember that mass doesn’t work like we want to think it does, just like time or light.
"by Newton's 2nd": well, Newton's 2nd does not apply in special relativity. In SR, the force has a parallel contribution F_// = γ³ma_// and a transverse contribution F_T = γma_T. Now, some old texts talk about "longitudinal" and "transverse" mass, but nowadays nobody talks in these terms. The object rest mass in an invariant (as it is given by the contraction the momentum 4-vector). The concept of "relativistic" (increasing) mass to match with Newton 2nd is an obsolete concept which is no more taught, which works only in some analogies. And the correct energy-mass relation for a moving body is not E=mc² but E=γmc².
Different velocity does not mean different speed, its like mean drift velocity of electrons in wires, their speed is greater than their velocity since they reflect of molecules within the material which gives an appearance of reduced speed, however it simply covers more distance due to this reflection
I think the trouble is convoluting reference frames. From any reference frame, nothing moves faster than light (at least nothing we can observe). So, if you are using the frame of a third party, observing two other parties each moving away from you close to the speed of light, it seems paradoxical that those two parties would be able to communicate with one another (this is a pedagogical paradox of relativity, and it's now well understood by physicists). However, from the reference frame of either of the first two parties, the other is moving away at a speed LESS than the speed of light, so communication should be possible.
So the answer to #16 may be correct, but the reasoning why is either wrong or else I did not understand the explanation.
Surely the easiest way to think about it is sure they’re moving away from each other but when the signal is sent from one to the other that light is now moving at the speed of light towards the other ship which is moving away at 0.9 times the speed of light. So it gains 0.1 light years per year on the other ship until it catches it. It would be very slow communication still but the trick is just because you’re travelling very quickly in one direction doesn’t mean light travels slower in the other direction when sending a signal.
Because the two ships in question 10 leave the same place, they are in the same relative position within the universe with regards to the expansion of the universe, so light speed communication will reach from one ship to the other.
However, there are stars that are far enough away that the expansion of the universe means that light speed will not theoretically ever reach these stars because they space between is expanding faster than the speed of light.
Does this imply that (if the star was still burning today), its light would never reach earth?
Are we only able to see the star's light because it was emitted in a time when the portion of the universe between us and the star wasn't expanding faster than the speed of light?
Good quiz. I do love the counter intuitive nature of much of modern physics. Although many (though not all) of these things do start to feel more sensible once you look deeper into them. A lot of the problem lies with how we commonly conceptualise things like matter, energy, space and time.
I guess that works too. Although the fact that the space between stars is expanding and therefore prevents any possible communication between them is fascinating, I believe the fact that you can't communicate with something that has exploded is also equally correct.
i’m not quite sure why the other answers to 13 are ‘wrong’ - if they’re sufficiently advanced then of course they could do it, by definition, and including the word ‘might’ means technically the other two could be correct. maybe if you changed it to ‘which of these do scientists now believe a computer may one day be able to do’?
I believe that the whole idea of a quantum computer is that it uses quantum particles to store info. I don't think this process would be useful in sending information instantaneously or predicting the future. While I guess it may be possible that we might have computers that can do either of these things, the fact that it says quantum computer implies that the question is looking for something a quantum computer specifically does.
I'm pretty sure randomness is considered to be a real thing that exists by most physicists, rather then it just being a result of us not knowing every variable.
So even with the most powerful computer that was able to account for every conceivable variable possible you wouldn't be able to predict the future to 100% accuracy
I think the singularity question is not really correct – my take on it would be singularities are where our current models break down. Wikipedia also says, "Physicists are undecided whether the prediction of singularities means that they actually exist (or existed at the start of the Big Bang), or that current knowledge is insufficient to describe what happens at such extreme densities."
Completely agreed and came to quibble over this too. I got the answer right because I knew what the QM wanted, but it isn't quite true.
If you are leaving finite / infinite as an unanswered question, it would be equally correct to say that the answer to "Can something have infinite density?" is "We don't know"
Does someone wanna explain how in 10.) we are able to communicate, even though the distance between the ships is expanding faster than light, but in question 16.) we can't for that exact reason?
Maybe my relativity is a bit off, but I took a modern physics class and I'm pretty sure that 16 is wrong isn't it?
The difference is that in the first case a distance is increasing, whereas in the second space itself is expanding. It's like the difference between two points moving across the surface of a balloon and the distance between two fixed points on the surface of a balloon increasing due to the balloon being blown up.
I think this quiz is quite good overall given the fact that it covers concepts that are difficult to understand and often misrepresented, however there are a few problems with the answers:
1. Energy can only become matter if it becomes an equal amount of ordinary matter and antimatter, by the conservation of the lepton number and baryon number.
5. Singularities are theorised but have never been directly observed, since they can only appear inside a black hole.
9. Again, an equal amount of ordinary matter and antimatter have to emerge simultaneously.
12. Not all interpretations of quantum mechanics agree on this point, though I am not knowledgeable enough in this area to explain what they do agree on. I believe that when one particle changes, apparently "causing" the other to change, this is not the result of any controllable process and so no causation can be proven (only correlation).
we assume that there is no law of physics that prevents an individual from living forever. I'm not sure whether predictions about the death of the universe rely on statistics or genuinely imply that the universe will inevitably end within a given period of time, but an assumption about this would need to be added to reach that conclusion.
1 and 9 are kind of nitpicking as you can argue that ordinary matter and antimatter are both types of matter, and 5 could be explained by adding that it is a prediction of theoretical physics and not observed. 12 and 14 need more assumptions that not all physicists agree on in order to be correct.
This is what happens with "theoretical" anything. It's just theory. The "big bang theory", the theory which is being used to discount creation, could not have happened everywhere at the same time. If that were true, then we'd always be in a constant state of explosion. The big bang theory at least says it originated from one point and radiated outward. The closest answer would be the center, but then again, we don't know the expansion rate of the universe, so we have no frickin idea.
It's not like the singularity that produced the Big Bang was one point suspended in empty space that exploded... it was (at least) the entirety of the observable universe. So saying that it happened at just one point in the observable universe would be inaccurate, even if that's easier for us to conceptualize.
If you've ever seen the Interesting Fact #65, "The Siberian town of Zheleznogorsk has a coat of arms that looks like this", which is a bizarre Russian bear on a bright red banner cracking an enormous with his caws, that's what's randomly showing up for me on this quiz.
for something to have infinite density, it must have 0 volume, hence it cannot exist, no? Without volume, it does not exist, in our 3D perception i guess, unless something can exist without volume
12/16, very fun and thought-provoking quiz. At first I wasn't sure for some of them like the many worlds theory but then it made sense to me and I thought it was kind of amusing
Of course, to even attempt to answer the question you have to clarify what is being asked. We can answer how big the observable universe is, for instance.
https://en.wikipedia.org/wiki/Universe
"The universe (Latin: universus) is all of space and time and their contents, including planets, stars, galaxies, and all other forms of matter and energy."
In question 7. you're referring to "relativistic mass" as just "mass". It gives the quiz-taker the false idea that an objects mass changes with time, which it does not. "Relativistic mass" is an abstract concept taught to students to simplify the inherently confusing nature of relativity, but that's it, a mathematical concept abstracted from reality.
Highly suggest everyone watch these two videos on the topic:
https://www.youtube.com/watch?v=WnLJoeBE_BM
https://www.youtube.com/watch?v=LTJauaefTZM
or read the following paper:
https://arxiv.org/pdf/hep-ph/0602037.pdf
I should really stop writing comments whilst sleep deprived...
However, there is no indication in the way the question is worded that this is referring to rest mass nor invariant mass.
If the observer measuring the mass of the object was in the same reference frame as the object, and thus not observing any change in mass, the observer would also ostensibly not be observing any change in the speed of the object. So, at least to me, the question is not misleading.
the universe makes no sense.
Remember E=mc^2 which absolutely applies here: as a mass approaches the speed of light, its energy increases, but this could be equivalently interpreted as an increase in mass, tending towards infinity.
Alternatively, as the object approaches the speed of light, the force required to accelerate it at a constant rate approaches infinity (because you need infinite energy to make a nonzero mass move at the speed of light). In this interpretation, because acceleration is constant and force approaches infinity, then by Newton’s 2nd, the object’s mass must be approaching infinity.
I think it’s important to remember that mass doesn’t work like we want to think it does, just like time or light.
It sure is weird though…
https://en.wikipedia.org/wiki/Double-slit_experiment
Two objects starting from the same spot can't move away from each other at faster than the speed of light.
But the space between objects can increase faster than the speed of light if space itself expands.
So the answer to #16 may be correct, but the reasoning why is either wrong or else I did not understand the explanation.
https://duckduckgo.com/?q=galaxy+faster+than+light
However, there are stars that are far enough away that the expansion of the universe means that light speed will not theoretically ever reach these stars because they space between is expanding faster than the speed of light.
Are we only able to see the star's light because it was emitted in a time when the portion of the universe between us and the star wasn't expanding faster than the speed of light?
Genuinely curious
So even with the most powerful computer that was able to account for every conceivable variable possible you wouldn't be able to predict the future to 100% accuracy
Apart from that, nice one!
If you are leaving finite / infinite as an unanswered question, it would be equally correct to say that the answer to "Can something have infinite density?" is "We don't know"
You mean because we have no way of telling wtf is at the center of a black hole right?
Maybe my relativity is a bit off, but I took a modern physics class and I'm pretty sure that 16 is wrong isn't it?
And there is another easy reason that we can't communicate with every star we see: some of them may already be destroyed since we are seeing the past.
1. Energy can only become matter if it becomes an equal amount of ordinary matter and antimatter, by the conservation of the lepton number and baryon number.
5. Singularities are theorised but have never been directly observed, since they can only appear inside a black hole.
9. Again, an equal amount of ordinary matter and antimatter have to emerge simultaneously.
12. Not all interpretations of quantum mechanics agree on this point, though I am not knowledgeable enough in this area to explain what they do agree on. I believe that when one particle changes, apparently "causing" the other to change, this is not the result of any controllable process and so no causation can be proven (only correlation).
14. This is only true if...
1 and 9 are kind of nitpicking as you can argue that ordinary matter and antimatter are both types of matter, and 5 could be explained by adding that it is a prediction of theoretical physics and not observed. 12 and 14 need more assumptions that not all physicists agree on in order to be correct.
Nurse!
https://www.jetpunk.com/interesting-facts/93