Kev M

The undisputed fact is that if time travel were actually possible then we would be getting inundated with calls. texts, emails saying..

" have you been affected by time travel ? .... please call xxxx solicitors...no win no fee "

8 hours ago, vlaiv said:

Well - there is this thought experiment - let's call it "If one could ride on a photon"  and it goes something like this: photon is traveling at the speed of light - so the rest of universe is traveling at the speed of light with respect to that photon in opposite direction.

Given that we have dilation of time for systems traveling very fast and when system is traveling at the speed of light - time slows down to a stop. Photon "sees" the rest of universe being effectively frozen in time. Whatever time "passes" in reference frame of that photon - it is irrelevant as nothing else could be used to time it - as everything else is at stand still - that leads to conclusion that no "effective" time flows in reference frame of a photon.

Extrapolation of this reasoning is that photon is just "energy transfer cord" between two space time coordinates - when particles exchange a photon they effectively "touch" across space and time (does this count as time travel? ).

That sounds like interesting reasoning, no "effective time" as no means of measuring , I am happier with that explanation than no time at all.

"touch"....👍

8 hours ago, vlaiv said:

Can you expand a bit on that please?

In most of the physics - energy is conserved so it can't be function of time.

 

c is a function of time , therefore E must be ?

1 hour ago, vlaiv said:

Actual formula goes like this:

Where m0 is rest mass

For photon with no rest mass above turns into

E = pc

Good explanation, that shows me where I misunderstood a bit....

However still have an issue with Photons, if they have energy and energy is a function of time.

The they must travel in time.....surely ?

22 minutes ago, iapa said:

It's, supposedly, an infinite universe.

Basing everything on that premise, everything is possible..............

Indeed if the universe was infinite, then not only is everything possible but everything actually happens....an infinite amount of time each.

Obviously the universe cannot be infinite.

2 hours ago, wulfrun said:

 E = mc², it will lead you to the proof. Any particle with no mass* is forced to travel at the speed of light and does not experience time.

So if m=0 then E=0

Therefore photons have no energy.....that cant be right.... or can it ?

2 hours ago, wulfrun said:

As for point-particles, I think the word "particles" is a bit misleading. It conjures up the idea of (say) tiny billiard-balls or some such, which is wrong because they couldn't be zero size. Just consider them as "things", with measurable properties.

Exactly my point, agree on this.

On 26/03/2022 at 09:12, iantaylor2uk said:

 Firstly, particles interact via fields, not through "touch". Electric and magnetic field are everywhere and interact in this way. 

The magnetic fields "touch" or interact in various ways....."touch" was easier to type.

On 26/03/2022 at 09:12, iantaylor2uk said:

Particles under certain circumstances act as point particles and under other circumstances as waves. 

"act as"..... so they are not actually point particles then ?

On 26/03/2022 at 09:12, iantaylor2uk said:

 Thirdly, it is experimentally obvious that photons do exist. I don't know where you got your definition of existence from, but photons can be created and destroyed, and time obviously passes for observers of the photons

Yep, generally agree with that.

On 26/03/2022 at 09:12, iantaylor2uk said:

 but time stands still for the photons themselves. 

That's the bit I have difficulty with.....and have still to find anything that proves this....plenty of statements but no proof.

If you could educate me on this it would be appreciated.

The worry with the OU is the costs in England.....£24,000 to complete this course.

Scotland is pretty much free or vastly reduced for the same course.

22 hours ago, iantaylor2uk said:

Physicists understand plenty about photons. Relativity shows that objects can travel through space and time, but if a particle travels at the speed of light (and only massless particles can) then those particles don't travel through time at all. So time stands still for photons, but they definitely exist.

I get the gist of what you are saying but it raises other issues around definitions as well.

For something to "exist" it has to "pass through" at least 2 moments in time ( debates around whether time is continuous or discrete does not matter in this case ).

By definition a "point particle" can not exist either.....a particle has to have dimension otherwise it is not a particle.....calling something a "point particle" is nonsense.

How can the position of a "point particle" be defined if it has no dimensions, how can it interact with anything if it cant "touch" anything

It can be called a waveform ( or similar ) and it can then possibly do these things but then it is not a "point particle".

And just to emphasise my points about nonsense.....

We cannot accurately measure the speed of light as we do not have a suitable "tape measure".

Consider the following....

We have decided we should all adopt the our individual Right Hand ( or your local speed of light) as the standard unit of measurement...

Measure your Right Hand (or your local speed of light) and see if it is the the same size as your standard unit of measurement.....

That's the problem....

11 hours ago, Mr Spock said:

There's no such thing as the present. Time is constantly moving forward so everything we perceive is in the past.

That's a tricky concept......

Would the moment of perception not be in the present ?

Even if that which was perceived was in the past ( which you are correct it would always have to be ).

Time can only travel in one direction....the paradoxes raised would make this obvious.

Anything that "stands still in time" by definition cannot exist.

Our understanding of the universe seems insufficient to deal with things like photons and their relationship with time ( or spacetime).

We are missing something.....

18 hours ago, iantaylor2uk said:

If you are a photon, time does not exist

Can a photon exist without time ?

To exist you would have to have a period of time to exist in.

There a Photon cannot exist...QED...

It is difficult to define length, as any measured object  exists in at least 2 different places in spacetime.

Consider two places A & B separated by a distance.

To measure this distance you have to put your ruler at A and then it takes a certain time to move your focus to B to read the measurement.

Currently the fastest time we can move our focus from A to B is the speed of light.

Obviously if A & B are moving relative to each other or to ourselves then results will vary.

However if we are happy to take both the speed of light and time as being universal constants then the metre can be accurately defined.

The problem is that to measure the speed of light we use.......light.....!

Its always going to give the same constant result.

On 30/01/2022 at 19:29, cajen2 said:

The next time I'm travelling at 90% of the speed of light, I'll let you know....😄

 

But if there are already galaxies travelling away from you at 99% the speed of light then they will see you as travelling at that speed.

And the Battle of Jutland wouldn't have happened yet.

( I know I shouldn't start sentences with "and or but"...  I don't care ).

23 minutes ago, cajen2 said:

BTW, the date of the Battle of Jutland is still fixed.....😉

Surely it would be dependant upon the speed of the observer .....🙃

On 13/01/2022 at 20:59, d-s-m said:

So I recently got my first telescope, and have just been using it in the garden so far. But now I'm thinking about getting out to some local stargazing spots such as nature reserves, remote car parks....etc. But I'm slightly concerned about spoiling the night vision of any other potential stargazers that might already be there when I arrive by car with the lights on, as I assume that most people will set up in the car park? 

I wouldn't worry about it, you cant drive with the lights off and if you do disturb anyone they are more than likely to be sympathetic when they find out you are observing as well.

What telescope did you get ?

Kev

I had one of them, wish I hadn't let it go, its a good scope.

Much better than the shorter focal length version.

1 hour ago, Ags said:

 Is there any evidence that dark matter interacts with fields and forces our type of matter doesn't? 

If their are fields and forces that our type of matter doesn't react with how would we know they exist, we would have no evidence of them  ?

4 minutes ago, wornish said:

I paid about £40 for a 50 Meter Ethernet cable and run that to my RPi on the Mount in the garden when I set it up.  Using VNC now just works! No pauses no drop outs. Wish I had done it long ago.  Trying to get a reliable WiFi connection just caused more frustration.

Sensible choice.....if it doesn't move, run a fixed cable to it.......wifi is just for portable things like phones, tablets etc.

Wifi causes lower speeds, higher latency and as mentioned, frequent disconnections.

Orthoscopics I would have thought ?

6 hours ago, SirSnackz said:

 

"While looking closely it appears that the Dec is moving and the RA is not."

I'm pretty sure I connected everything correctly seeing as I'm able to use the hc and slew the mount through that in both RA and Dec. But I will double check

I would triple check this...are the Dec & RA reversed ?

There is one on Thingiverse

Finderscope adapter Skywatcher for Datyson camera guiding by Fixoo - Thingiverse

Kev

Superb video........😀

The standard 8x50mm seems to be popular, there are adapters available that allow you to reach focus with a guide cam ( gpcam or similar ).

There are also purpose built guide scopes of around 50mm, which are basically the same but have reduced focal length and come complete with adapters.

I assume the dovetail for the 50mm is the same size base as the smaller guide scope you already have ( plenty of owners on this site to confirm )