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/sci/ - Science & Math

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4409411 No.4409411 [Reply] [Original]

If the sun were to suddenly vanish (instantly) would we be able to observe the effects of no heat/light, or no gravity first?

>> No.4409413

same time

>> No.4409419

>>4409413

Wrong, idiot. 5/10.

>> No.4409424

>>4409419

explain?

>> No.4409432

>>4409424

Gravitational waves do not exceed the speed of light hurrdurr.

>> No.4409433

>>4409411
No gravity instantly, no heat/light for 8 minutes

>> No.4409440

>>4409433

0/10.

>> No.4409445

>>4409432

I said the same time? Gravitational waves propogate at c do they not?

>> No.4409447

same time, nothing that carries information can travel faster than the speed of light

>> No.4409449

The answer to the following question clearly is assumed to be obvious but...

Who is we, and by what methods of perception and observation?

>> No.4409453

While gravity would change at the same time the heat/light is more quickly observable. This is because we would need to wait some time t before we could observe the effect the effects that gravity had, where we could measure the change in light instantly.

>> No.4409467

>>4409445

They do not.

>> No.4409468

>>4409433

why do you say no gravity instantly? can you point me to some research on what happens if a gravity "source" disappears suddenly?

I think we on earth would notice the lack of light/heat long before we realize the sun has no gravity.

>> No.4409469

But does gravity travel like light? What if gravity recedes from the earth instead of receding from the sun first like light?

>> No.4409472

the gravitational field propagates at c....

>> No.4409476

>>4409467

Troll detected.

>>4409468

Yes dumbass, the research is entitled general relativity, look into it sometime. That's like pants-on-head retarded.

>> No.4409478
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4409478

The answer is the same time.

>> No.4409480

>>4409469

lolwut. If troll 5/10.

>> No.4409494

Same time. Nothing travels faster than light.

>> No.4409497

http://www.youtube.com/watch?v=hByJBdQXjXU
I can haz science?

>> No.4409501

>>4409476

so you're saying that the gravity effects would be felt instantly?

>> No.4409510

>>4409501

They would be felt in 8 minutes, the same time as light.

>> No.4409523

If nothing moves faster than the speed of light, then wouldn't gravity be felt some x amount of time after (although it'd probably be a negligible difference)?

>> No.4409532

>>4409527

>neutrinos

don't travel faster than light

>> No.4409535

>>4409453
This. The light intensity from the sun would change rapidly and intensly. Our ability to measure the gravity change relies on two derivatives of the gravity. While this would be measurable, it would take more time to detect it.

>> No.4409540
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4409540

>>4409535
Forgot image

>> No.4409543 [DELETED] 

>>4409535

the intensity wouldn't change for 8 minutes

>> No.4409550

>>4409543
Both would change at the exact same time. Because the intesnity changes faster that the position of a sample particle in a gravitational field, it is more quickly measured.

>> No.4409556

>>4409535
Wouldn't the earth go flying off into space if the gravity of the sun were to suddenly disappear? If we had instruments ready and waiting, it would be the same time. If not, I think humans would notice the earth flying off in a direction than it has gone throughout our entire evolution just as much as when the lights went out. All-in-all: Fucking Terrifying.

>> No.4409560

>>4409556

see

>>4409550

>> No.4409579

For the record gravitational waves are not waves that propagate gravity they are something more niche.

>> No.4409592

ITT: trolls
I was thinking 6/10-ish for OP but I wasn't sure of the intention, then I saw Einstein on the picture, so 3.5/10, may or may not troll again

>> No.4409612 [DELETED] 

>>4409579
haven't a clue what sort of crackpottery has taken place in this thread, but you got to be fucking kidding me.

you're telling us that
<div class="math">W(T) = - \frac{1}{2} \int \frac{d^{4} k }{(2 \pi)^{4}} T^{\mu \upsilon}(k)^{*} \frac{(G_{\mu \lambda} G_{\upsilon \sigma} + G_{\mu \sigma} G_{\upsilon \lambda}) - \frac{2}{3} G_{\mu \upsilon} G_{\lambda \sigma}}{k^{2}-m^{2} + i \epsilon} T^{\lambda \sigma}/eqn]
does not describe the interaction between two lumps of stress energy?</div>

>> No.4409622

>>4409579
haven't a clue what sort of crackpottery has taken place in this thread, but you got to be fucking kidding me.

you're telling us that
<div class="math">W(T) = - \frac{1}{2} \int \frac{d^{4} k }{(2 \pi)^{4}} T^{\mu \upsilon}(k)^{*} \frac{(G_{\mu \lambda} G_{\upsilon \sigma} + G_{\mu \sigma} G_{\upsilon \lambda}) - \frac{2}{3} G_{\mu \upsilon} G_{\lambda \sigma}}{k^{2}-m^{2} + i \epsilon} T^{\lambda \sigma}</div>
does not describe the interaction between two lumps of stress energy?

>> No.4409625

>>4409612

What are your parameters?

>> No.4409627

>>4409625

meant

>>4409622

>> No.4409705 [DELETED] 

Really? Gravity propagates at c? Have they even measured that yet?

Going to Google it but if anyone has good links I'd like to look at them

>> No.4409732

I've always hated this so-called thought experiment.

It's impossible for something to just "vanish". What does he even mean by that?

His other thought experiments, like riding a bicycle near the speed of light, are also preposterous, but at least we see where he's coming from.

"Well, you can't literally travel near the speed of light on a bicycle, but I can imagine some sort of spacecraft going at relativistic speeds."

But no, the "vanishing" sun makes no sense whatsoever. It doesn't demonstrate a theoretical limit like the speed of light, it's just nonsense.

It's an "immovable object vs unstoppable force" question.

>> No.4409739

>>4409732

What do you mean it doesn't demonstrate anything? It demonstrates that the "flow" of information has a finite speed, the speed of light. How does that not demonstrate anything? Certainly, the premise is preposterous, but it still illustrates an important topic.

>> No.4409749

>>4409739
It's asking a question about the effects of something which absolutely cannot happen.

We shouldn't ask "what would happen if the sun suddenly vanished?", we should ask a different, physically-possible question.

"What would happen if the sun zoomed away from us at near the speed of light?" or "What would happen if the sun collapsed into a black hole?" are both highly unlikely, but at least possible.

>> No.4409769

>>4409732

The disappearing sun thing was never conceived as a thought experiment, but rather as a simple situation where you can see clearly, without requiring a lot of equations, the difference between an instantaneous and a moving gravitation: in one case the orbit would break immediately, in the other it would keep turning until the gravitation wave hit the planet. Of course, the actual calculations are not based on scenarios involving disappearing stars.

Another problem many people have is that what does it matter how gravity behaves when stars disappear, since they don't. I see where these people are coming from. There are other, more realistic contexts where it makes a difference, they are simply more complex to treat. On of them is binary star systems: when two objects rotate around each others, their combined gravitation is greater when they are aligned with you, and lower if they are side by side relative to you, BUT if gravitation is not instantaneous then there's some delay between their position and their gravitational effect on you. This has important effects.

The immovable object vs. unstoppable force thing is a situation where the entities are defined so as to be mutually incompatible. They cannot both exist at the same time. The disappearing object is not self-contradictory like that. It's just a very simple model, that assumes an extreme scenario so as to analyse its effects. Whether stars can disappear like that or not is irrelevant to the point it tries to make.

>> No.4409770

>>4409749

>"What would happen if the sun zoomed away from us at near the speed of light?"

That is equally preposterous. Instead of removing something from existence spontaneously, you are creating massive amounts of energy from nothing.

>> No.4409799

>>4409770
"Instead of removing something from existence spontaneously, you are using massive amounts of energy to move a star that's fine where it is. Oh, this is still theoretical? I guess you can use that much energy if you want."
fixed

>> No.4409810

>>4409799

But the whole point YOU are opposed to is making impossible things happen for the sake of the example.

A star disappearing or infinite energy appearing. I don't see how your idea is preferable.