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Cause of death: Electromagnetic radiation or the effect of the gravitational wave?

Egalitarianism Always

By Egalitarianism Always,
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Egalitarianism Always Squire

Egalitarianism Always

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To not derail the other thread:

If the Sun explodes, would our planet be obliterated by:

a ) the electromagnetic radiation first,

or

b ) by the effect of the gravitational wave caused (which move at the speed of light) pulling our planet towards it at the same time, thus creating a combined speed faster than light. Think what happens to the ocean at the seashore before a tsunami hits.

Or maybe something else I haven't thought of?

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Kalbear Council Member

Kalbear

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To solve this:

there is no 'expanding gravitational pulling effect' or anything of the sort, and there's no math that would show that there is. Gravity does create waves, but even massive collisions cause incredibly tiny ripples. It wouldn't matter in the least.

Nor is gravity 'speeding towards anyone at the speed of light'. 

The short answer is that 'it depends' - largely on whether or not the explosion is symmetrical or not. If it's symmetrical, gravity doesn't change at all until literally a microsecond before the mass of the explosion and the light of the explosion hits the earth, because until then gravitational forces at a reasonably far distance act as a point source. As it gets much closer to earth, you'll start experiencing tidal effects depending on what part of the earth you're on, but you won't really have time to notice.

If it is NOT a symmetrical explosion - which is more likely - then quickly the earth turns into a very nonfunctional spaceship, and can do so fairly quickly. Maybe - depending on whether or not gravity propagates at the speed of light or instantaneously. In GR it does so via the speed of light, so even any asymmetry would cause it to do exactly what happens anyway - the effect would hit you at the same time a massive amount of electromagnetic radiation would. 

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Egalitarianism Always Squire

Egalitarianism Always

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50 minutes ago, Kalbear said:

To solve this:

there is no 'expanding gravitational pulling effect' or anything of the sort, and there's no math that would show that there is. Gravity does create waves, but even massive collisions cause incredibly tiny ripples. It wouldn't matter in the least.

Tiny ripples were detected by us from events 3 BILLION light years away, let that sink in.  The pulling effect of gravitational waves, you'd have to be able to understand the scientific papers of B.P Abbot et al.

In terms you might understand the gravitational pulling effect is very real, according to LIGO the gravitational waves that they detected at the source was the gravitational wave they observed was 2.3 solar masses, which is an absolutely mind-boggling amount of energy. If you were too close, the rapidly fluctuating tidal forces on your body would cause alternating compressive and tensile stresses on your body, tearing your body to bits, which would certainly count as a "macroscopic effect".  0.5 solar mass or three solar masses, makes no difference when you're as close as we are to our sun.

Sure, at an appropriate distance, you'd still be able to feel the gravitational wave without being killed. However, with such an enormous amount of energy being released this close together by astronomical standards, for the experience to be survivable you'd have to be so far away that you wouldn't really be able to "observe the event with the naked eye."

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there is no 'expanding gravitational pulling effect' or anything of the sort, and there's no math that would show that there is. Gravity does create waves, but even massive collisions cause incredibly tiny ripples. It wouldn't matter in the least.

Incorrect, see the scientific facts I just gave.

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Nor is gravity 'speeding towards anyone at the speed of light'. 

Gravitational waves move at the speed of light, again a scientific fact.  Do you even know what a gravitational wave is?  Let it sink in what they are.

Quote

The short answer is that 'it depends' - largely on whether or not the explosion is symmetrical or not. If it's symmetrical, gravity doesn't change at all until literally a microsecond before the mass of the explosion and the light of the explosion hits the earth, because until then gravitational forces at a reasonably far distance act as a point source. As it gets much closer to earth, you'll start experiencing tidal effects depending on what part of the earth you're on, but you won't really have time to notice.

As always it's symetrical as is the assumption in all physics experiments unless explicitly stated otherwise.  I see you use the word tidal forces, well done, see above; also the assumption about who notices even if it's matter of a second or even less it's the cause of death.

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If it is NOT a symmetrical explosion - which is more likely - then quickly the earth turns into a very nonfunctional spaceship, and can do so fairly quickly. Maybe - depending on whether or not gravity propagates at the speed of light or instantaneously. In GR it does so via the speed of light, so even any asymmetry would cause it to do exactly what happens anyway - the effect would hit you at the same time a massive amount of electromagnetic radiation would. 

An asymmetrical explosion could easily lead to a worse situation than a 'better' one.

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Kalbear Council Member

Kalbear

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20 minutes ago, Egalitarianism Always said:

Tiny ripples were detected by us from events 3 BILLION light years away, let that sink in.  The pulling effect of gravitational waves, you'd have to be able to understand the scientific papers of B.P Abbot et al.

It doesn't matter (though I do understand them, thx), because the effect of the waves are incredibly small AND they propagate at lightspeed.

20 minutes ago, Egalitarianism Always said:

In terms you might understand the gravitational pulling effect is very real, according to LIGO the gravitational waves that they detected at the source was the gravitational wave they observed was 2.3 solar masses, which is an absolutely mind-boggling amount of energy. If you were too close, the rapidly fluctuating tidal forces on your body would cause alternating compressive and tensile stresses on your body, tearing your body to bits, which would certainly count as a "macroscopic effect".  0.5 solar mass or three solar masses, makes no difference when you're as close as we are to our sun.

Again, at lightspeed, and again, this was the effect of two black holes colliding - several orders of magnitude heavier than our sun. 

20 minutes ago, Egalitarianism Always said:

Sure, at an appropriate distance, you'd still be able to feel the gravitational wave without being killed. However, with such an enormous amount of energy being released this close together by astronomical standards, for the experience to be survivable you'd have to be so far away that you wouldn't really be able to "observe the event with the naked eye."

Again, it's the sun. It cannot by nature make particularly large gravitational waves, and the waves do not dissipate in strength particularly much. 

20 minutes ago, Egalitarianism Always said:

Incorrect, see the scientific facts I just gave.

You didn't give any facts, but good try.

20 minutes ago, Egalitarianism Always said:

Gravitational waves move at the speed of light, again a scientific fact.  Do you even know what a gravitational wave is?  Let it sink in what they are.

I do. Obviously you didn't read the paper. 

20 minutes ago, Egalitarianism Always said:

As always it's symetrical as is the assumption in all physics experiments unless explicitly stated otherwise.  I see you use the word tidal forces, well done, see above; also the assumption about who notices even if it's matter of a second or even less it's the cause of death.

Symmetrical is an assumption in experiments, and is usually wrong. Regardless it doesn't particularly matter, as you'll absolutely be obliterated by the lightwave, and the gravitational wave will not affect you in any real way. Here's the important thing to consider here: no matter what, the effect of the explosion will never travel faster than the expanding light wave, and will never happen earlier (and will almost certainly happen a few microseconds later). That it also cannot be particularly stronger than one solar mass is important, as you will once again not feel it. 

Here's the real issue you don't seem to understand about gravity - having a gravitational effect of 2.6 solar masses is interesting, but it is not particularly strong. You don't typically feel the Sun's pull on you here, nor do you feel the moon's pull to any degree. Not only do you have to be incredibly close to have gravity pull you at any degree of importance, but it has to have an asymmetrical effect. With the sun's wave, it'll all be coming from the same direction and have the same tensor, meaning that the relative force on your body will be identical. 

 

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