LSAT and Law School Admissions Forum

Get expert LSAT preparation and law school admissions advice from PowerScore Test Preparation.

 Rachael Wilkenfeld
PowerScore Staff
  • PowerScore Staff
  • Posts: 1419
  • Joined: Dec 15, 2011
|
#98731
Paragraph 3, quan-tang, explains why we would expect the high entropy universe to begin with. Paragraph 5 is explaining a different answer---how did we end up with a low entropy starting point if it should have been a high entropy universe? But before we even get to the issue in paragraph 5, we need to establish what we would expect the universe to look like. That's explained in paragraph 3.
User avatar
 benndur
  • Posts: 13
  • Joined: Aug 28, 2024
|
#111656
KelseyWoods wrote: Mon Jul 29, 2019 2:10 pm
Paragraph 5 doesn't tell us why we are more likely to have a high entropy initial condition than a low entropy one. It simply tells us that it is possible to have a big bang-like occurrence in a high entropy condition. So paragraph 5 supports why, even in a high entropy initial condition, we could still have a big bang occurrence.

Hope this helps!
Forgive me if this sounds arrogant, but this is wrong.

Paragraph 5 says:
"Recent research has shown that even empty space has faint traces of energy that fluctuate on the subatomic scale. Physicists Jaume Garriga and Alexander Vilenkin have suggested that these fluctuations can generate their own big bangs in tiny areas widely separated in time and space. Carroll and Chen take our universe, and others, to be such fluctuations in a high entropy multiverse."
This paragraph basically boils down to:
[In our universe (high entropy)]: Empty (universal) space (low entropy) -> Fluctuations -> Big Bang (Tiny: creates traces of energy)
Therefore maybe similarly =>
[In the "multiverse" (high entropy)]: Empty (multiversal) space (low entropy) -> Fluctuations -> Big Bang (Big: creates our universe)

Empty space is a low entropy condition. Entropy is mostly related to states/configurations, and with nothing in it, empty space is thus highly ordered with essentially zero possible states (ignoring quantum fluctuations).

Without any outside knowledge, we know empty space is low entropy because of the example they describe in Paragraph 3, where a room increases in entropy when objects within in are randomly moved about, thus increasing the "disorder" compared to a neatly arranged "moderately orderly" room.

Imagine a clean room no objects or furnishings. There wouldn't be any way to increase the disorder by randomly moving things about into a more disordered state, because there's nothing inside. Intuitively just as a clean room is highly ordered compared to a messy one with things randomly strewn about, a room with nothing in it is even more ordered than an organized room.

The high entropy that is being referred to in paragraph (5) is the entropy of the multiverse. The idea here is that in our own (high entropy) universe, we see traces of energy emerge as fluctuations from empty space (low entropy) on atomic scale. So maybe on a larger scale, our universe started out as a fluctuation of a (high entropy) multiverse in some region of low entropy (empty space).

Thus paragraph 5 doesn't explain how high entropy conditions can still create a big bang. It instead suggests one way it might be possible that in low entropy conditions, a big bang could occur, which is the opposite of what you've stated (that it supports why in a high entropy initial condition a big bang might occur).

But high/low entropy isn't really what paragraph 5 is concerned with, since the passage states that a hot dense universe is also low entropy. The difference is that it is full of matter, and intuitively a "big bang" can follow from this. So what it's really getting at is how a universe with nothing in it could have produced something.

This means that paragraph 5 does actually give support to the hypothesis of cold empty space as a possible starting condition, by suggesting how it might be that the big bang could arise from empty space. The problem though is that it's only a suggestion/possibility, and doesn't make cold empty space a likely initial condition.

C) is a better answer because paragraph 4 explains that entropy is a measure of "total disorder" and that it increases with time. Since it increases with time, it must have been at its absolute lowest at the beginning. When considering the messy room example and how it relates to disorder, this strongly supports the idea that it would be likely that the starting condition would resemble cold empty space; this is the state of lowest entropy and highest order. There is nothing in the room that can be randomly repositioned to create a less orderly state: cold empty space.

The really confusing part is that they tell us that a hot and dense universe = low entropy, and this naturally leads you to expect that cold and empty would = high entropy, but this is not true. A hot and dense universe is low entropy mostly because of the density, as there are few configurations that can occur in the same way that the atoms in a solid have few configurations compared to a gas. But empty space is even lower entropy than this. If we to go back again to the example of the room, the hot dense universe would be like a tiny room housing an immovable lava lamp. The matter inside the lamp hot and dense, but confined to a single space and thus the room is low entropy. Despite this, the matter inside the lava lamp can still move within the lava lamp so the entropy is not lower than an empty room.

Very nasty question. Sorry for the wall of text.

Get the most out of your LSAT Prep Plus subscription.

Analyze and track your performance with our Testing and Analytics Package.