Everything is relative(or maybe not)

How physics changed our human perspective

Dap Hartmann

Astronomy1979 – 2003

Leiden UniversityHarvard-Smithsonian Center for Astrophysics

Radioastronomisches Institut, Universität BonnMax-Planck-Institut für Radioastronomie

Innovation & Entrepreneurship2003 – present

TU Delft

It doesn't matter how beautiful your theory is, it doesn't matter how smart you are. If it doesn't agree with experiment, it's wrong.

− Richard Feynman

Length is relative

1 meter =• (1927) Length of the platinum ‘standard meter’ (at 0°C and 1

atm)accuracy: ?

• (1960) 1,650,763.73 wavelengths of the 605 nm Krypton-86 spectral line accuracy : 0.005 – 0.01 µm (10−8)

• (1983) Distance that light travels in a vacuum in 1 ⁄ 299,792,458 seconds

accuracy : 0.1 nm (10−10)

Length is relative

Time is relative

1 second =• (1956)   1 ⁄ 31,556,925.9747 of a ‘tropical year’

1 second is 1/60 of a minute 1 minute is 1/60 of an hour 1 hour is 1/24 of a day 1 day is 1/365.242347 of a year

= 365 days, 5 hours, 49 minutes and 1.114 seconds.

• (1967) 9,192,631,770 periods of a Cesium-133 hyperfine

transition = atomic clock

Time is relative

Train: 100 km/h (w.r.t. the observer)

-5 km/h (w.r.t. the passenger)Passenger: 5 km/h (w.r.t. the train)

105 km/h (w.r.t. the observer)

Velocity is relative

5 km/h

100 km/h

The passenger moves w.r.t. the train 5 km/hThe train moves w.r.t. the Earth 100 km/hThe Earth rotates around its axis 1600 km/h @ equatorThe Earth rotates around the Sun 108,000 km/hThe Sun rotates in the Milky Way 828,000 km/hThe Milky Way moves w.r.t. the Local ClusterThe Local Cluster moves w.r.t. the local Supercluster … Super-Supercluster …

Absolute Velocity?

The only thing thatAstronomersreceive fromthe Universeis Light(in all wavelengths)

(1983 Definition)

≡ 299,792,458 meter per second(in a vacuum)

Speed of Light

Michelson, Pease & Pearson (1930–35) • 1.6 km long vacuum tube• Rotating mirror• Light beam travels back and forth 10 times• Accuracy: 11 km/s

Moon1 light second

Sun8 light minutes

Proxima Centauri4.2 light years

Alberan60 light years

Speed of Light

Hungarian Revolution (November 1956)

Advantages of its finiteness:• Looking back in time

Disadvantages of its finiteness:• (Super) Computers• High Frequency Trading• “Hello, we are HERE!”

TV transmission of the 1936 Olympic Games in BerlinContact (1985) : Vega is at a distance of 25 light years.

• Interplanetary communicationAstronaut on Mars, 270 million km (= 15 light minutes)

from Earth

Speed of Light

Light is a wave ‘so’ it needsa mediumto propagate in:

the Ether.

The Michelson-Morely experiment (1887)

Possible explainations:• Experimental error• The Earth drags along the ether• There is no ether• The Earth is stationary• Length contraction

No effect was observed!

• Object are at rest or have a constant rectilinear motion • There are no forces present (so also no acceleration!)

Inertial frame (of reference)

“The laws of motion are the same in all inertial frames.”

− Galileo Galilei (1632)

“The laws of physics are invariant (identical) in all inertial systems.”

− Albert Einstein (1905)

Inertial frame• Object are at rest or have a constant rectilinear motion • There are no forces present (so also no acceleration!)

Relativity Postulate (1905)“The speed of light in a vacuum is the same for all observers, regardless of the motion of the light source.”

Consequences of theSpecial Theory of Relativity

• Time dilation• Length contraction• Relativity of simultaneity• Universal speed limit• Relativistic mass• E = mc2

Time dilation

If v = 0.1 c then t’ = 1.005 tIf v = 0.5 c then t’ = 1.15 tIf v = 0.75 c then t’ = 1.51 tIf v = 0.9 c then t’ = 2.29 tIf v = 0.95 c then t’ = 3.20 tIf v = 0.99 c then t’ = 7.09 t

Applies to: • Time• Length ( 1/γ )• Mass

γ ≥ 1.0001 when v ≥ 0.01414 c0.01% increase when v = 4,242 km/s = 15,271,200 km/h

Lorentz Factor

Twin Paradox

Simultaneity is relative

1 gram of matter is equivalent to 9 x 1013 J25 GWh

92% H + 8% He

One 4He atom is 0,7% lighter than four 1H atomsE = 26,73 MeV

Number of nucleons in nucleus

Thank you!