<p>In a very real and fundamental way &quot;This can't happen&quot;  Not only practically (you can't make the sun disappear)  But in a fundamental way, you can't make mass disappear.</p>
<p>Even if you suddenly converted all the mass of the sun into energy, that energy would still have a gravitational effect.  And removing the mass of the sun, at speeds greater than the speed of light fundamentally breaks the very physical laws which you need to base any answer on.</p>
<p>So this is a frame challenge answer. It is theoretically impossible to make mass disappear.</p>

CC BY-SA 4.0
2020-08-05T20:56:22.763Z
Black hole, traveling at 0.99c, having the same radius as the sun, slams smack dab into into it. Not at all likely, but not illegal. It'd probably turn all the inner planets into smears though.
Wayfaring Stranger
CC BY-SA 4.0
2020-08-05T21:21:47.940Z
Then there is mass moving at less than light speed, appoaching this sun and then leaviing **at less than light speed** fundamentally and importantly ***Mass can't disappear***  This is not a just a practical fact, but critical to general relativity.  If the mass-energy of the sun could leave at more than light speed, then GR is completely wrong.
James K
CC BY-SA 4.0
2020-08-05T23:58:27.113Z
Right. I'm not disagreeing with that, just pointing out that the gravitational field of the sun could be made to nearly disappear quite rapidly.
Wayfaring Stranger
CC BY-SA 4.0
2020-08-04T21:58:37.293Z
2020-08-04T21:58:37.293Z
James K
<p>I found my answer <a href="https://en.wikipedia.org/wiki/Cosmic_catastrophe" rel="nofollow noreferrer">here</a> :</p>
<p>it seems my question was already has been answered by Albert Einstein.it's called <strong>cosmic catastrophe</strong>.
according to that page In Einstein's spacetime model, the disappearance of the sun would create gravitational waves in the spacetime. The gravitational waves <strong>travel at the speed of light</strong>, and an orbiting planet would not react to the sun's disappearance until after the gravitational wave has reached it. Only then, the planet would start to travel in a straight line.</p>
<p><strong>Update to my answer:</strong></p>
<p>The first direct observation of gravitational waves was made on 14 September 2015 and was announced by the LIGO and Virgo collaborations on 11 February 2016</p>
<p><a href="https://en.wikipedia.org/wiki/First_observation_of_gravitational_waves" rel="nofollow noreferrer">https://en.wikipedia.org/wiki/First_observation_of_gravitational_waves</a>
So it was not just proven although has been measured as well</p>

CC BY-SA 4.0
2020-08-04T20:56:50.233Z
Direct measurement of the speed of gravitational waves are still a little sparse: https://en.wikipedia.org/wiki/Speed_of_gravity Somewhere *near* lightspeed seems most reasonable.
Wayfaring Stranger
CC BY-SA 4.0
2020-08-05T06:33:06.363Z
thanks for your link, now i should have more question about gravity during inflation :)
Pouya Samie
CC BY-SA 4.0
2020-08-04T17:30:18.753Z
2023-04-26T13:01:06.740Z
2023-04-26T13:01:06.740Z
Pouya Samie
<p>As we know by General Relativity, gravity propagates by the speed of light c = 299,792,458 m/s in a vacuuum (like space).</p>
<p>The average distance between the earth and sun is about 149.6 million kilometers, so it takes light about 8.3 minutes from the sun to earth.</p>
<p>This means, if the sun were to disappear right now, we would have to wait 8 minutes and 20 seconds until we would realize. Luckily, by all known laws of physics, this is not possible :)</p>

CC BY-SA 4.0
2020-08-04T17:32:13.453Z
thank you for your answer I just found my answer and it's still magnificent that means with no mass we can have gravity effect.
Pouya Samie
CC BY-SA 4.0
2020-08-04T17:30:11.467Z
2020-08-04T17:30:11.467Z
jng224
<p>Imagine if the Sun disappears right now. When the Earth will be affected by its absence? Does it affect immediately, or it takes almost 8 minutes? (The time that light travels from the Sun to the Earth.)</p>
<p>So if I ask this question in another way, the changes in Space-Time will affect immediately or it will travel by light speed?</p>

<gravity><space-time>
If the Sun disappears right now, when the absence of its gravity affects on Earth?
Pouya Samie
# If the Sun disappears right now, when the absence of its gravity affects on Earth?

(Asked by: username_0 on 2020-08-04)

Imagine if the Sun disappears right now. When the Earth will be affected by its absence? Does it affect immediately, or it takes almost 8 minutes? (The time that light travels from the Sun to the Earth.)

So if I ask this question in another way, the changes in Space-Time will affect immediately or it will travel by light speed?

**Tags:** gravity, space-time


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## 3 answers

### Answer by username_3 on 2020-08-04. Score: 5 | Accepted answer

As we know by General Relativity, gravity propagates by the speed of light c = 299,792,458 m/s in a vacuuum (like space).

The average distance between the earth and sun is about 149.6 million kilometers, so it takes light about 8.3 minutes from the sun to earth.

This means, if the sun were to disappear right now, we would have to wait 8 minutes and 20 seconds until we would realize. Luckily, by all known laws of physics, this is not possible :)

> **Comments:**
> **username_0**: thank you for your answer I just found my answer and it's still magnificent that means with no mass we can have gravity effect.  

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### Answer by username_1 on 2020-08-04. Score: 3

In a very real and fundamental way "This can't happen" Not only practically (you can't make the sun disappear) But in a fundamental way, you can't make mass disappear.

Even if you suddenly converted all the mass of the sun into energy, that energy would still have a gravitational effect. And removing the mass of the sun, at speeds greater than the speed of light fundamentally breaks the very physical laws which you need to base any answer on.

So this is a frame challenge answer. It is theoretically impossible to make mass disappear.

> **Comments:**
> **username_2**: Black hole, traveling at 0.99c, having the same radius as the sun, slams smack dab into into it. Not at all likely, but not illegal. It'd probably turn all the inner planets into smears though.  
> **username_1**: Then there is mass moving at less than light speed, appoaching this sun and then leaviing **at less than light speed** fundamentally and importantly ***Mass can't disappear***  This is not a just a practical fact, but critical to general relativity.  If the mass-energy of the sun could leave at more than light speed, then GR is completely wrong.  
> **username_2**: Right. I'm not disagreeing with that, just pointing out that the gravitational field of the sun could be made to nearly disappear quite rapidly.  

---

### Answer by username_0 on 2020-08-04. Score: 3

I found my answer [here](https://en.wikipedia.org/wiki/Cosmic_catastrophe) :

it seems my question was already has been answered by Albert Einstein.it's called **cosmic catastrophe**.
according to that page In Einstein's spacetime model, the disappearance of the sun would create gravitational waves in the spacetime. The gravitational waves **travel at the speed of light**, and an orbiting planet would not react to the sun's disappearance until after the gravitational wave has reached it. Only then, the planet would start to travel in a straight line.

**Update to my answer:**

The first direct observation of gravitational waves was made on 14 September 2015 and was announced by the LIGO and Virgo collaborations on 11 February 2016

<https://en.wikipedia.org/wiki/First_observation_of_gravitational_waves>
So it was not just proven although has been measured as well

> **Comments:**
> **username_2**: Direct measurement of the speed of gravitational waves are still a little sparse: https://en.wikipedia.org/wiki/Speed_of_gravity Somewhere *near* lightspeed seems most reasonable.  
> **username_0**: thanks for your link, now i should have more question about gravity during inflation :)  

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