# The Naked Scientists Forum

### Author Topic: Massless Existence  (Read 4115 times)

#### Xin

• Jr. Member
• Posts: 23
##### Massless Existence
« on: 12/12/2006 22:22:53 »
If I remember correctly, some people say that light/photons are massless, and that they travel so fast because it would otherwise take an infinite amount of energy to move at that speed if photons did have even a tiny mass. So this got me thinking about other massless "things" such as gravity, time, and the thoughts in my mind. Even though we can't physically SEE gravity, we can see its effects such as the apple falling to the ground...and we can't see the thoughts in someone's head, but we can see the effects of people's decisions.

But light...if light really is massless, we shouldn't be able to see it, so what effect from the photons are we seeing that causes "light"? I figured it would be friction as the photons rip through space, but then we'd also experience a great deal of heat too, right? And if the photon is massless, how could it even cause friction in the first place? So what exactly is the "light" that we are seeing? Or am I looking at this totally wrong? Thanks!

#### Soul Surfer

• Neilep Level Member
• Posts: 3345
• keep banging the rocks together
##### Re: Massless Existence
« Reply #1 on: 13/12/2006 00:00:46 »
WE can only "see" photons by destroying them and converting the energy that they contain into something else for example an electrical signal  in some special cirumstances it is possible to convert only part of the energy out of a photon and leave another photon with a lower energy (lower frequency travelling in the same direction

#### Xin

• Jr. Member
• Posts: 23
##### Re: Massless Existence
« Reply #2 on: 13/12/2006 01:34:37 »
I'm confused. How can you destroy something that has no mass?

#### daveshorts

• Moderator
• Neilep Level Member
• Posts: 2583
• Physics, Experiments
##### Re: Massless Existence
« Reply #3 on: 13/12/2006 07:49:31 »
we can't see light, we can just see it's effects, just like gravity. It's effects just happen to be exiting the optical pigments in our retina, which sends a signal to our brain.

Why does something have to have mass to be destroyed?

#### Xin

• Jr. Member
• Posts: 23
##### Re: Massless Existence
« Reply #4 on: 13/12/2006 19:24:27 »
I figure that in order to be able to physically touch something or alter it, it would have to have mass. I mean, we can't destroy gravity or time nor can we manipulate it (not to my knowledge anyways). I can't think of any massless "object" that can be destroyed.

#### Heliotrope

• Sr. Member
• Posts: 151
##### Re: Massless Existence
« Reply #5 on: 13/12/2006 22:02:25 »
Something that is massless isn't an object.
It's pure energy.
Photons are energy only. They have no mass.

No one knows what gravity really is just the same as no one knows what time really is.
There is a lot of good and relevant information but there are far, far too many unknowns about them for concrete conclusions to be drawn.
You're best off not including either of these things in the discussion as you're not going to be able to get any hard facts out of them.

If I remember correctly, some people say that light/photons are massless,

It's not "some" people.
It's the entire scientific community and anyone else who can reason properly.
Photons have no mass.

Quote
So this got me thinking about other massless "things" such as gravity, time, and the thoughts in my mind.

The extent of current thinking does not permit conclusions about what gravity is made of. There isn't enough information.
String Theory suggests that there are such things as gravitons but at present there is no way to test the predictions so they remain in the realm of hypothesis and conjecture. Strings themselves are pure conjecture and have no foundation in observed reality. We need experiments to see if they actually exist or not.
No one has the slightest idea what time is so assuming that whatever it is made of, assuming it's made of anything at all, is a bit premature.
It's like you assuming you know what colour my socks are even though you have never met me, have no idea what my taste in socks is and you've never seen me. It's an unwarranted assumption. Best not assume things about things we don't know anything about.

As for the thoughts in your mind, well they definitely have energy and mass.
Your thoughts are composed of electrical impulses and chemical reactions that happen inside your brain.
Electrons have mass and energy. The chemicals involved in the reactions have mass and energy.
So basically thoughts have mass.

Quote
But light...if light really is massless, we shouldn't be able to see it,

This isn't right at all.
What makes you assume you shouldn't be able to see it ?
Have you assumed that something without mass cannot exist ?

Photons have energy dependent upon their wavelength.
That energy is absorbed by the chemicals in your retina and those chemicals take the energy and convert it into a little pulse of electrons. They convert the energy of the photon into electrical energy.
That electrical energy, electricity, travels down your optic nerve and finally gets to your brain where it's interpreted as part of an image.

The bottom line is that you can't see a photon. You can only detect the electrical energy that it is converted into in your retina.
Personally I can't think of any way in which it's possible to actually see a photon.
You certainly can't do it with an eye at any rate.

Quote
so what effect from the photons are we seeing that causes "light"?

See above.

#### Heliotrope

• Sr. Member
• Posts: 151
##### Re: Massless Existence
« Reply #6 on: 13/12/2006 22:08:34 »
I mean, we can't destroy gravity or time nor can we manipulate it (not to my knowledge anyways).

It is simplicity itself to manipulate gravity and also time.

Get yourself a housebrick or something else that's heavy.
Put it on a table in front of you.
Look at it.
It's a brick.
You have just aletered the local gravitational field around the table by adding mass to it.
You can alter gravity by moving mass around.
You are warping spacetime when you move the brick around. You are warping spacetime when you move anything around.

Ready for time manipulation now ?

Get outside.
Look around for a mountain.
Get your climbing boots on and get yourself to the top of the mountain.
Nice view ?
Good.
You are now experiencing time at a different rate than the people at the foot of the mountain because you are higher up in the Earth's gravity well.
From point of view of the people at the foot of the mountain, time is passing faster for you than it is for them.
Granted the effect will only amount to some femtoseconds difference but it is there and it is measurable. Rather easily measurable in fact.

Easy huh ?

« Last Edit: 13/12/2006 22:10:14 by Heliotrope »

#### Xin

• Jr. Member
• Posts: 23
##### Re: Massless Existence
« Reply #7 on: 14/12/2006 01:55:40 »
Excellent! Thank you Helio. I understand now :)

#### Heliotrope

• Sr. Member
• Posts: 151
##### Re: Massless Existence
« Reply #8 on: 16/12/2006 01:47:56 »
Cool.
[8D]

#### The Naked Scientists Forum

##### Re: Massless Existence
« Reply #8 on: 16/12/2006 01:47:56 »