I cant grasp the notion that a particle that is known to exist, dosent have some kind of mass. If it exist it has to have some kind of mass however small.

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Old James

A photon has no rest mass. A neutrino must have one but it is very small.

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A photon is a disturbance in the electo-magnetic fields. Nothing travels; just like a wave in a football stadium. The wave travels (a disturbance) but nothing actually moves around the stadium--just the wave.. Because it can be focused and "Aimed" precisely it is said to behave like a particle.

A wave can have energy, however, and hence an equivalent mass. Is dark matter simply an imputed mass from the energy that we have trouble accounting for in Astrophysics ?

A photon of sufficient energy emits an electron when hitting a solid. This is the photoelectric effect for which Einstein received his only Nobel prize. So, even if a photon travels like a wave. it acts as a particle when it is absorbed. This is the wave-particle duality postulated by Louis de Broglie, which was the starting point of quantum mechanics.
Tullio

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Einstein said: it is theory that determines what can be observed. ...

I agree.

We can all "see" an image with our eyes. However, there is also a lot of understanding and 'world knowledge' needed to then be able to interpret and appreciate what that image is showing.

Likewise, for designing and understanding real-world experiments. The verification between our understanding and a real-world experiment is a two-way process that lets our understanding converge ever more closely to the reality we experience.


Keep searchin',
Martin

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See new freedom: Mageia Linux
Take a look for yourself: Linux Format
The Future is what We all make IT (GPLv3)

Look, and you just may find it.

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Member of the People Encouraging Niceness In Society club.

It's there they just need to find it.

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If a photon has no rest mass. Then how can a black hole prevent a photon from escaping its gravity.
And can dark matter be sucked in to a black hole? I just cant think in the abstract on some of these quantum physics ideas.

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Old James

I guess that is what the better minds than ours' is trying to work out James.

Their papers sort of make sense but they always leave me with a headache while trying to read them (just like some politicians). :-(

Sorry but for some of us, we prefer smaller more understandable words being used.

Cheers.

A photon is simply following the curvature of space-time created by massive objects such as stars, galaxies and black holes. I saw on Italian RAI3 TV a talk by an Italian astronomer woman who had discovered the first double pulsar in the records of the Parkes radiotelescope in Australia. There was a delay in the reception of the radio impulse emitted by the pulsars because the wave had to follow the curvature of space-time created by the companion pulsar.
Tullio

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It's there they just need to find it.

They think it's there, and they think they may or may not find it. That's a lot of unknowns Lynn! I tend to think that it isn't there, but I'd be more than happy to be proved wrong, it can only increase my own knowledge, which is a good thing.

It is there, they just have troubles naming it, that's why they call it 'dark'

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rOZZ
Music
Pictures

through.the.wormhole.s01e08.beyond.the.darkness

The above link, to a ~40 min video on YouTube, is a pretty good primer on Dark Energy/Matter.

Thanks for the link, it's not working for me.

[edit]

This video contains content from Discovery Communications, who has blocked it in your country on copyright grounds.

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http://www.youtube.com/watch?v=9bc7NYs02yQ

Through the Wormhole- Dark Matter

Shorter you tube. This man thinks dark matter is in another universe.

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Thanks for the link, it's not working for me.
[edit]

This video contains content from Discovery Communications, who has blocked it in your country on copyright grounds.

The link doesn't work from the US or UK.
Does work from an Amsterdam or Brussels IP address.
Google sure does work hard to keep Government and Corporate bosses happy.
i'll try to find a stream that works in the US/UK.

Thanks :)

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Through the wormhole s01e08 Beyond the Darkness

The above link seems to work from a Washington IP address.
Maybe ok in the US.

Nice try and thanks. Wants a download.

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Nice try and thanks. Wants a download.

At first it wanted to download some media player HD.
i have NoScript add-on to Firefox running.
Didn't download any file, just kept allowing more permission till finally the video would play.
Not sure if it's wise to punch holes in your firewall even if only temporary.

If interested a download from torrent only takes 20 mins.

Nice try :)

Not going to take a chance.

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http://map.gsfc.nasa.gov/universe/uni_matter.html

What is the Universe Made Of?

Yes, the title changed. Dark energy, can't be found. Yet, 72 % of the universe is made up of dark energy.

Occams Razor, thing going on with both the matter/energy.

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Yes, the title changed. Dark energy, can't be found. Yet, 72 % of the universe is made up of dark energy.

Suspected to be the cause of the universe expanding.

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The Kite Fliers

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Kite fliers: An imaginary club of solo members, those who don't yet
belong to a formal team so "fly their own kites" - as the saying goes.

Yes, the title changed. Dark energy, can't be found. Yet, 72 % of the universe is made up of dark energy.

Suspected to be the cause of the universe expanding.

Let me add=> and that at an increasing rate.

Thanx for changing the thread title Lynn:) I was going to suggest that.

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rOZZ
Music
Pictures

Yes, the title changed. Dark energy, can't be found. Yet, 72 % of the universe is made up of dark energy.

Suspected to be the cause of the universe expanding.

Let me add=> and that at an increasing rate.

Thanx for changing the thread title Lynn:) I was going to suggest that.

Your welcome, Julie :)

Then the question is, where is the universe expanding to. Is it going to go out with a Wimper, or a Bang??

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