# The Naked Scientists Forum

### Author Topic: If the Sun travelled at c towards Earth, how long before it arrives?  (Read 1215 times)

#### Thebox

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##### If the Sun travelled at c towards Earth, how long before it arrives?
« on: 30/06/2016 10:42:07 »
As title question.

added - after pausing for thought, another question, what time does it arrive?

added - I may have it a bit backward, but relatively we see the sun in its past, so how can the past catch up with the present?

added- I think the Sun would show 12:08 am while the Earth clock shows 12, but hopefully you get the question.
« Last Edit: 30/06/2016 10:54:20 by Thebox »

#### jeffreyH

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##### Re: If the Sun travelled at c towards Earth, how long before it arrives?
« Reply #1 on: 30/06/2016 11:03:34 »
The relativistic mass of the sun would be infinite so I suggest throwing the laws of physics out of the window and taking up a creative writing course.

#### Thebox

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##### Re: If the Sun travelled at c towards Earth, how long before it arrives?
« Reply #2 on: 30/06/2016 11:08:19 »
The relativistic mass of the sun would be infinite so I suggest throwing the laws of physics out of the window and taking up a creative writing course.

I am not quite sure how that answers the question , I was rather hoping for some maths for the answer.

Seemingly the Sun could strike the Earth and we would not notice it had even moved because of the light/sight delay of 8 minutes.  Something seems to be flawed unless I am misunderstanding something?

#### jeffreyH

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##### Re: If the Sun travelled at c towards Earth, how long before it arrives?
« Reply #3 on: 30/06/2016 11:17:51 »
The relativistic mass of the sun would be infinite so I suggest throwing the laws of physics out of the window and taking up a creative writing course.

I am not quite sure how that answers the question , I was rather hoping for some maths for the answer.

Seemingly the Sun could strike the Earth and we would not notice it had even moved because of the light/sight delay of 8 minutes.  Something seems to be flawed unless I am misunderstanding something?

You are absolutely correct. Since the sun would be traveling at the same speed as the photons it would appear to an observer (at a safe distance. ie another universe  ) that the sun had moved instantaneously from its initial position to its final position next to the earth.

#### Thebox

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##### Re: If the Sun travelled at c towards Earth, how long before it arrives?
« Reply #4 on: 30/06/2016 11:27:39 »
The relativistic mass of the sun would be infinite so I suggest throwing the laws of physics out of the window and taking up a creative writing course.

I am not quite sure how that answers the question , I was rather hoping for some maths for the answer.

Seemingly the Sun could strike the Earth and we would not notice it had even moved because of the light/sight delay of 8 minutes.  Something seems to be flawed unless I am misunderstanding something?

You are absolutely correct. Since the sun would be traveling at the same speed as the photons it would appear to an observer (at a safe distance. ie another universe  ) that the sun had moved instantaneously from its initial position to its final position next to the earth.
Hmm, interesting somebody agrees with something I said, thanks.  You have failed to discuss the times though?

If it is 12am on Earth I see the Sun as it were at 11:52pm?

So at example 12:000000000000000000000000000001am, the Sun could instantly kill me by collision and I would not see it coming literally because it is already on its way and as already travelled most of the distance I am not even aware of?

#### jeffreyH

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##### Re: If the Sun travelled at c towards Earth, how long before it arrives?
« Reply #5 on: 30/06/2016 11:36:27 »
If we wish to move a mass at 1 metre in 1 second then the force can be derived from the mass alone. So that increasing the mass is a direct reflection of the increase in the required force. If we make the mass infinite then the force required to move it is infinite. Since the gamma function produces an infinite mass at the speed of light we can show a relationship between these two situations. In the first we are increasing the inertial mass in order to affect the magnitude of the force required. In the second we are increasing the relativistic mass which achieves a similar result. The difference between the two is that the first is governed by newtonian mechanics and the second by relativistic mechanics.

#### jeffreyH

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##### Re: If the Sun travelled at c towards Earth, how long before it arrives?
« Reply #6 on: 30/06/2016 11:39:18 »
The relativistic mass of the sun would be infinite so I suggest throwing the laws of physics out of the window and taking up a creative writing course.

I am not quite sure how that answers the question , I was rather hoping for some maths for the answer.

Seemingly the Sun could strike the Earth and we would not notice it had even moved because of the light/sight delay of 8 minutes.  Something seems to be flawed unless I am misunderstanding something?

You are absolutely correct. Since the sun would be traveling at the same speed as the photons it would appear to an observer (at a safe distance. ie another universe  ) that the sun had moved instantaneously from its initial position to its final position next to the earth.
Hmm, interesting somebody agrees with something I said, thanks.  You have failed to discuss the times though?

If it is 12am on Earth I see the Sun as it were at 11:52pm?

So at example 12:000000000000000000000000000001am, the Sun could instantly kill me by collision and I would not see it coming literally because it is already on its way and as already travelled most of the distance I am not even aware of?

The mathematics for this situation are undefined by definition but technically you are going in the right direction.
« Last Edit: 30/06/2016 11:42:03 by jeffreyH »

#### Thebox

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##### Re: If the Sun travelled at c towards Earth, how long before it arrives?
« Reply #7 on: 30/06/2016 11:43:04 »
If we wish to move a mass at 1 metre in 1 second then the force can be derived from the mass alone. So that increasing the mass is a direct reflection of the increase in the required force. If we make the mass infinite then the force required to move it is infinite. Since the gamma function produces an infinite mass at the speed of light we can show a relationship between these two situations. In the first we are increasing the inertial mass in order to affect the magnitude of the force required. In the second we are increasing the relativistic mass which achieves a similar result. The difference between the two is that the first is governed by newtonian mechanics and the second by relativistic mechanics.

Sorry Jeff I am struggling to see the relationship to your post and the topic, I am also struggling today to understand what you are on about, I do understand when you say a infinite force to move an infinite mass but other than that I am lost to your intent and the relationship.

added - or are you trying trying to say it is impossible to move the Sun type thing?

#### Alan McDougall

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##### Re: If the Sun travelled at c towards Earth, how long before it arrives?
« Reply #8 on: 30/06/2016 12:44:31 »
It would arrive later than expected, how much later , that is a moot point.

#### IAMREALITY

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##### Re: If the Sun travelled at c towards Earth, how long before it arrives?
« Reply #9 on: 30/06/2016 15:57:37 »
The relativistic mass of the sun would be infinite so I suggest throwing the laws of physics out of the window and taking up a creative writing course.

I am not quite sure how that answers the question , I was rather hoping for some maths for the answer.

Seemingly the Sun could strike the Earth and we would not notice it had even moved because of the light/sight delay of 8 minutes.  Something seems to be flawed unless I am misunderstanding something?

You are absolutely correct. Since the sun would be traveling at the same speed as the photons it would appear to an observer (at a safe distance. ie another universe  ) that the sun had moved instantaneously from its initial position to its final position next to the earth.
Hmm, interesting somebody agrees with something I said, thanks.  You have failed to discuss the times though?

If it is 12am on Earth I see the Sun as it were at 11:52pm?

So at example 12:000000000000000000000000000001am, the Sun could instantly kill me by collision and I would not see it coming literally because it is already on its way and as already travelled most of the distance I am not even aware of?

Pretty much...

Thankfully, as Jeffrey has referenced, such a scenario need not keep us up at night, since it would take an infinite amount of force to move the sun that fast to begin with...

I would also wager that the sun would've killed you long before 12:00000000...1 am...  But you still wouldn't have seen it comin...

#### Colin2B

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##### Re: If the Sun travelled at c towards Earth, how long before it arrives?
« Reply #10 on: 30/06/2016 21:37:23 »
I'm assuming the sun starts its journey at 1152 - that is the time on both the sun and earth. At 1152 Earth is seeing the light which left the sun at 1144.
If we assume the sun accelerates instantaneously to light speed and ignoring relativistic mass effects, then the sun along with its light and heat will all arrive together at 1200. There would be no warning.

Of much greater interest is the question "what caused this?"

PS I'm ignoring the photosphere which would arrive marginally before the sun's surface.

« Last Edit: 30/06/2016 21:40:27 by Colin2B »

#### Thebox

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##### Re: If the Sun travelled at c towards Earth, how long before it arrives?
« Reply #11 on: 01/07/2016 10:13:27 »

Of much greater interest is the question "what caused this?"

I am subjecting you to my thinking............................caused ''this''

#### alancalverd

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##### Re: If the Sun travelled at c towards Earth, how long before it arrives?
« Reply #12 on: 01/07/2016 10:22:29 »
You are absolutely correct. Since the sun would be traveling at the same speed as the photons it would appear to an observer (at a safe distance. ie another universe  ;D) that the sun had moved instantaneously from its initial position to its final position next to the earth.

Not true unless the observer was in the line of travel of the sun. From a position at 90 degrees to that line, the sun would be seen to move.

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##### Re: If the Sun travelled at c towards Earth, how long before it arrives?
« Reply #12 on: 01/07/2016 10:22:29 »