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- Ice Core
- a cylindrical section of ice retrieved from snow packs or glaciers that have formed over several hundreds or thousands of years.
- Indirect Evidence
- the use of logical and rational outcomes from other direct evidence in order to conclude that there is support for a hypothesis. Our archeologist might use that same clay jar as indirect evidence that the civilization used jars to store food.
- Infrared
- this band of the electromagnetic spectrum has wavelengths in the micron (μm, `10^-6m`) range. They are correspondingly more energetic than microwaves and radio.
- Initial (default) Value
- the starting value for a variable. Without a starting value, a computer program may be behave in unexpected ways when it comes time to use a variable that has no default value.
- Inner Solar System
- the region of space that is smaller than the radius of Jupiter’s orbit around the sun. It contains the asteroid belt as well as the terrestrial planets, Mercury, Venus, Earth and Mars.
- Intermediate Black Hole
- a black hole with mass on the order of tens or hundreds of solar masses that are typically observed near, but not at, the centers of distant galaxies.
- Intrinsic
- in science, the intrinsic value or property of an object does not change based on outside factors. For example, your mass, or the amount of stuff of which you are made, does not change whether you are standing on Earth or the Moon. Mass is an intrinsic property of yours. Your weight, which is related to your mass by the force of gravity will be different whether you measure it on Earth or on the Moon.
- Input
- the values that are fed into a computer program from a user or perhaps a sensor, for example, a temperature sensor.
- Inverse Compton Scattering
- in a collision between a low-energy photon and an electron in a high-energy state, the electron can transfer energy to the photon as it transitions to a lower energy state.
- Ionized
- the term for an atom which has lost one or more electrons causing it to become positively charged.
- Ions
- an atom or molecule that has a net positive or negative electric charge due to the loss or gain of electrons.
- Irregular Galaxies
- these are the galaxies that do not fit into any of the other three categories.
- Isotopes
- isotopes of a given atom differ in the number of neutrons in their nucleus. Using carbon as an example, the most common isotope has six protons and six neutrons in the nucleus. But there is a different isotope that has six protons (that’s what makes it carbon) and seven neutrons. Both isotopes behave the same in chemical reactions. Other elements can also have different numbers of neutrons, and thus will have different isotopes. The chemical behavior of different isotopes of a given atom is always the same.
- Isotropic
- looks the same in every direction.
