Why does space lack conventional directional distinctions such as up/down, left/right, and forward/backward?
### Dark Matter and Dark Energy **Dark Matter**: 1. **WIMPs (Weakly Interacting Massive Particles)**: Hypothetical particles interacting via weak nuclear force and gravity. Evidence includes gravitational effects unexplained by visible matter. 2. **Axions**: Extremely light particles potentially solRead more
### Dark Matter and Dark Energy
**Dark Matter**:
1. **WIMPs (Weakly Interacting Massive Particles)**: Hypothetical particles interacting via weak nuclear force and gravity. Evidence includes gravitational effects unexplained by visible matter.
2. **Axions**: Extremely light particles potentially solving quantum chromodynamics issues. Indirect evidence from astrophysical observations.
3. **Sterile Neutrinos**: Hypothetical non-weak-interacting neutrinos, supported by some cosmological observations.
**Dark Energy**:
1. **Cosmological Constant (Λ)**: Constant energy density explaining the universe’s accelerating expansion, evidenced by Type Ia supernovae.
2. **Quintessence**: Dynamic field varying over time, with potential but lacking strong observational support.
### Promising Exoplanets and Their Characteristics
**Key Characteristics**:
1. **Size and Mass**: Earth-sized or super-Earths.
2. **Composition**: Rocky planets.
3. **Atmosphere**: Capable of supporting liquid water.
4. **Distance from Star**: Within the habitable zone.
5. **Stellar Type**: Stable, long-lived stars (G-type, K-type).
**Significant Discoveries**:
1. **Proxima Centauri b**: In Proxima Centauri’s habitable zone.
2. **TRAPPIST-1 System**: Seven Earth-sized planets, three in the habitable zone.
3. **Kepler-452b**: In the habitable zone of a Sun-like star.
4. **LHS 1140 b**: Super-Earth with a stable orbit in the habitable zone.
### Detection Methods
1. **Transit Method**: Observes star dimming during planet transit.
2. **Radial Velocity Method**: Measures star’s wobble due to orbiting planets.
3. **Direct Imaging**: Captures images of exoplanets.
4. **Spectroscopy**: Analyzes light for atmospheric composition.
### Future Missions
**James Webb Space Telescope** and **European Extremely Large Telescope** will enhance atmospheric studies and habitable planet identification.
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Direction in Space: In space, the concepts of left, right, up, and down lose their meaning because there is no fixed frame of reference. On Earth, these directions are defined relative to gravity and our planet's surface, providing a consistent reference for orientation. Gravity pulls us towards theRead more
Direction in Space:
In space, the concepts of left, right, up, and down lose their meaning because there is no fixed frame of reference. On Earth, these directions are defined relative to gravity and our planet’s surface, providing a consistent reference for orientation. Gravity pulls us towards the ground, making “down” relative to our position, while “up” is the opposite direction, and left and right are relative to our forward direction.
However, in the microgravity environment of space, especially in orbit around Earth or in deep space, there is no single force like gravity to define a universal “down.” Astronauts and objects float freely, and orientation becomes relative to one’s position and point of view. Without a fixed point of reference, the conventional directions of left, right, up, and down do not apply. Instead, astronauts use relative positioning based on their spacecraft or local structures to navigate and communicate direction.
This relativity of direction in space requires astronauts to adapt to a new way of thinking about orientation and movement, relying on visual and situational cues within their immediate environment rather than any absolute reference points.
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