Alien Artifacts

If you recognized the significance of the objects, you'd realize that this probe was sent from Earth. The probe is a tutorial for extraterrestrials, like the interstellar explorer, teaching the understandings of our physics. The clues are the collection of items, each of which is used for determining one of our standard physical units.

The laser allows calculation of distance. Our base (metric) unit for distance is the meter. A meter is defined as the distance light travels in 1/29979245 of a second. Why not 1/30000000 of a second? Previously, a meter had been defined as 1,650,763.73 wavelengths of the red-orange line of the spectrum of krypton-86. Prior to that, it was defined by marks on a physical bar of platinum-iridium. The goal of the redefinition was to come up with a physical definition that could be precisely measured, remain constant, and was a close a possible to the previous definition. The historical basis of the meter was ~1/10,000,000 of the distance from the North Pole to the equator.

The metal cylinder represents the kilogram. Presently, the standard calibration for the kilogram is a cylinder of platinum-iridium kept at the International Bureau of Weights and Measures in Paris. A near-identical copy exists in the United States at the National Bureau of Standards. The kilogram is the only metric unit still defined by measure against a real object.

The water defines temperature. The Kelvin degree is 1/273.16 of the temperature at which water transitions between solid liquid and gas, also referred to as the triple point.

The black box is a timer, blinking off seconds. The second is defined as "the duration of 9,192,631,770 cycles of the radiation associated with a specified transition of the cesium-133 atom" (from the National Bureau of Standards).

The collection of metal plates would describe how these items are used to calculate our constants and our system of mathematics. Together, these would give an alien race the knowledge necessary to understand our system of sciences, and potentially communicate scientific knowledge with us.