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Lecture 3

ASTA02H3 Lecture Notes - Lecture 3: Gravitational Constant, Fundamental Interaction, Kelvin


Department
Astronomy
Course Code
ASTA02H3
Professor
Diana Valencia
Lecture
3

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ASTA02- Lecture 3 (Jan. 15th)
Topics
- FUNDAMENTAL FORES
- MATTER
- SPECTRA. INTRODUCTION
Light is the only “signal” we get from far away galaxies
All interactions in nature are ruled by four fundamental forces:
- Gravitational
- Electromagnetic
- Strong nuclear
- Weak nuclear
GRAVITATIONAL FORCE:
- Gravitation binds masses over long distances
- Weakest force of nature
- Long-range attractive force
- Obeys the Inverse Square Law of Distance:
. F= GM1M2/d2
- Gravitational constant: 6.67408 × 10-11 m3 kg-1 s-2
ELECTROMAGNETIC FORCE
- Acts between charged particles
- Like charges repel each other
- Opposite charge attract each other
- Long- range, inverse-square law force:
. Binds electrons and protons into atoms
. Binds atoms together into molecules
- EM force is very strong: 10^39 times stronger than gravity
STRONG AND WEAK NUCLEAR FORCE
- Short-range force (< 10^-15) in atomic nuclei
STRONG FORCE:
- Binds quarks inside protons and neutrons
- Binds protons & neutrons into nuclei
- Strongest force of nature
WEAK FORCE:
- Responsible for radioactivity
- Second weakest force
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